TakeASeat
If you see it like that I guess. I think I said that she wasn't close with her brother though. Chapter 88 was when they talked about her brother and whatnot. MC's appearance initially triggered guilt in her as she wasn't a good sister so she decides to treat MC well as if he was her younger brother. Then she realizes that her feelings are too strong and aren't normal siblings. So initially it was kind of like that but then her perspective about it changed. Again, people view things through their own lens so it's up to you.